Soil:plant relationships of species-rich Molinia caerulea dominated communities of the Culm Measures, North Devon, with special reference given to phosphorus cycling

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Abstract

A semi-natural community known locally as Culm grassland in Devon and N. E. Cornwall
is under threat from agricultural improvement, abandonment and inappropriate management
In the last fifty years 87% of the original area has been lost. Further loss may be prevented
by an examination of the factors that influence the plant community and how they may be
manipulated by management. Thus the research described in this thesis addressed the soil
conditions and the plant communities, with particular reference to phosphorus cycling.
In 1992 a preliminary characterisation of soil nutrient and water conditions, and species
composition was conducted on a pristine Culm grassland, an improved grassland and a
formerly abandoned Culm grassland. A significant elevation in soil extractable phosphorus
was found in mid-April in response to fertiliser applications on the improved grassland.
Similarities with previous research and an absence of a similar pattern in mineral nitrogen
prompted a detailed investigation of phosphorus dynamics in 1993. A better indication of
plant 'available' P was found by removing soil solution directly using novel methods of
centrifuging and suction cups. Environmental conditions were highly influential. Low
concentrations of P in suction cup solutions on Culm grassland indicated that Culm species
may remove P at very low concentrations. An investigation of the above-ground biomass
found that the uptake of P was highest in M. caerulea. M. Caerulea also influenced the
return of P to the soil via organic matter through the production and subsequent breakdown
of large quantities of litter. Additions of P to turfs caused a perturbation by enhancing the
uptake of P by M. caerulea and increasing P fixation.
The data was employed to produce a schematic model of the Culm grassland which
identified input and outputs, storage compartments and transfers within the P cycle. This
contributed towards making management recommendations for a range of Culm grassland
communities which may be maintained, improved or recreated.

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All items in PEARL are protected by copyright law.
Author manuscripts deposited to comply with open access mandates are made available in accordance with
publisher policies. Please cite only the published version using the details provided on the item record or document.
In the absence of an open licence (e.g. Creative Commons), permissions for further reuse of content should be
sought from the publisher or author.